It is well known in motor vehicles to provide an air bag module mounted to a steering wheel. A typical driver's side air bag module includes a generally circular inflator positioned partially within a bag opening of an air bag for discharging inflator gas to inflate the air bag upon sensing certain predetermined vehicle conditions. The undeployed air bag is folded atop the inflator and a module cover overlies the air bag, inflator and other module components.
The air bag module is formed as a separate and independent unit from the steering wheel. The cover, air bag, and inflator are each securely anchored to a base plate of the module such that inflation forces can be withstood. In addition, the module typically includes a plurality of axially elongated mounting members extending downwardly from the base plate for connecting the module to a mounting portion of a steering wheel.
The cover of the air bag module overlies the air bag, inflator and other module components to form an aesthetically pleasing cover which is durable for normal vehicle use. The cover commonly has tear lines or weakened portions that allow the cover to open during air bag inflation. It is known to connect the cover of the air bag module to the base plate by a plurality of fasteners, such as rivets or screws. The use of multiple fasteners increases assembly time.
The prior art has also suggested attachment of the cover by the use of mating overlapping tabs on each of the cover and base plate. However, assembly is still difficult since the tabs on the base plate are rigid metal which must be bent or crimped into place. The suggestion has also been made to form tabs on the cover with inwardly and upwardly turned J-shaped hooks on the tabs which are inserted into mating holes in the base plate. However, the hooks on the tabs are not sufficiently thick to securely maintain the cover to the base plate during inflation since the hooks must be thin enough to be inserted through the holes during assembly. Since the hooks do not tightly fit in the holes, they are free to pull out of the holes under the forces of air bag inflation. Thus, the prior art has taught adding additional components to the module such as a snap-in-place ring that acts as a spacer to fill the holes to prevent removal of the hooks from the holes during air bag inflation.